An independent investigation into the death of a prisoner at the Royal Lancaster Infirmary has concluded.
The investigation followed the death of Derek Macdonald, 35, at the hospital in January.
A spokesperson for Lancashire Police said: "We were called at 5.13pm on 25th January this year to the Royal Lancaster Infirmary hospital to support prison officers who were already present guarding Mr Macdonald, a prisoner, who had become unwell and agitated.
"Lancashire Police officers arrived at 5.20pm and supported HM Prisons colleagues in restraining the man.
"At 5.27pm Mr Macdonald’s medical condition worsened, and he stopped breathing and became unconscious.
"He was given CPR, but he was sadly pronounced dead a short time later at 6.30pm.
"Following enquiries, a prison officer in his 30s, was arrested on 31st January on suspicion of manslaughter.
"He was released under investigation but has now been told he will face no further action.
"This follows a full and thorough investigation of the circumstances surrounding Mr Macdonald’s death.
"Our thoughts remain with his loved ones. His family have been told of the latest developments.
"The matter will now proceed to inquest.
"The incident was referred to the Independent Office for Police Conduct, and they carried out an independent investigation solely into the role of the police during this incident.
"They concluded that no police officer was at fault and closed their investigation."
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